Just keep yourself logged in so you dont have this issue.
I don't think that will work unless you keep your same IP forever will it?
I'm using Bitcointalk on mobile through my home wi-fi, public wi-fi, mobile data and I don't have to login each time when I switch IP.
And maybe some people have their own reasons why they don't want to keep account always logged in. One reason mentioned by jackg, another reason is security - if computer used by several person for example it's not very safe to keep account always logged in.